1. Field of the Invention
This invention pertains generally to the field of bioconversion, and more particularly to a bioconversion container which may be used for Intermodal cargo transport and alternatively for bioconversion of matter.
2. Description of the Related Art
While landfill space is dwindling or becoming more costly or distant, industrial and municipal waste production is increasing. Furthermore, an ever-increasing variety of materials are developed and introduced into the waste stream. Consequently, the safe disposal of liquid, sludge and solid waste is continually more challenging and complex.
Composting, which, for the purposes of this disclosure will be defined as “the use of living, aerobic and or anaerobic microbial organisms to convert solids and liquids into more environmentally safe and/or beneficial by-products,” is a potentially viable alternative to landfills for the disposal of organic materials from nearly all waste streams. Composting can be used, for example, to process municipal wastewater biosolids, to remediate industrial wastewater solids, and to treat wastes and by-products from processing food and agricultural products. Composting can reduce the volume of organic waste materials by 50% or more, yielding a stable, non-odorous material that can be used as fertilizer or as an amendment for soil.
Before about 1970, composting was typically a simple process in which waste materials were piled and allowed to sit until they decomposed. It was most frequently done on a small scale and was not often considered for industrial-scale problems. Grinding the material to be composted was considered advanced technology.
An advance in composting technology came from the realization that adding air to the composting mixture could increase the efficiency of composting. The microbes that produce compost require air and will smother inside of a static unaerated pile. Hence, the initial methods of aeration involved moving or agitating the compost to allow air into the stack.
A typical example of this aeration is a windrow turner that picks up the compost and dumps it to one side. Many municipal composting sites are currently windrow turner operations, though process control is, unfortunately, quite primitive. Piles are typically turned at the convenience of the operator, rather than to optimize the composting process. A typical pile of compost will use all of its oxygen within about one-half hour, so such windrow turning is seldom related to actual oxygen demand. Turning is done seldom enough that microbes in the center of the pile are rapidly depleted, and the center of the pile stops composting. Turning the pile merely re-inoculates the center material with fresh microbes, and composting continues in the center of the pile for another one-half hour when the oxygen supply is, once again, depleted. Unfortunately, the repeated mechanical actions that are required for turning destroy some beneficial fungi that rely on large, filamentous growth. In addition to the oxygen and mechanical problems introduced by a windrow system, composting with windrow turners is typically done in an open, unsheltered area. The vagaries of weather and rainfall most often determine the water content of the composting mass. When there is too little rain, the pile is too dry. When there is too much rain, the pile is wet and requires frequent turning. Too much rain can also lead to problems with runoff of leachate.
One method used to overcome some of the disadvantages of pile composting is to enclose compost piles in a building. An enclosure that keeps rain off of the compost allows better regulation of water content. However, such a facility is very expensive. Furthermore, with pile composting, various irritating and potentially toxic gases are sometimes produced. Since operators must enter the enclosure to maintain the composting process, enclosing compost also involves maintaining the quality of large volumes of air within the building. Without high-quality and high-quantity air handling systems, the atmosphere within an enclosure can be irritating, if not toxic, to an operator.
Some of the disadvantages of pile composting are overcome by more modern reactor vessel processes. By design, the reactor vessel is typically only slightly larger than the compost which it contains. This reduces the land area required to store the compost during the composting process. In addition to reduced land area, the total volume containing or enclosing the compost is also reduced. Lower total volume means reduced air handling requirements. Furthermore, in-vessel reactors also provide the opportunity for collection of potentially odorous emissions. The compost is enclosed, and exhaust air may be routed through a filtration system. This separation of operator from compost air benefits the health and safety of all operators. There are other benefits, beyond land space and air handling, from reactor vessels. Handling and mixing, which is required in all systems, can also be mechanized using reactor vessels, and the compost is enclosed.
In-vessel systems may be used not only for composting, but also for other bio-conversion processes. Bioconversion describes the conversion of matter using biological processes either wholly or at least in part. While not limited solely thereto, bioconversion includes not only such processes as aerobic and anaerobic composting, but also bio-filtration, bio-remediation and other biological conversions.
While bioconversion processes may be conducted in very small laboratory containers, to be of economic value these processes require large vessels or containers. Nevertheless, these processes are still performed in relatively few locations and so the demand for such vessels or containers is relatively small. Consequently, many artisans have designed custom containers and have fabricated these custom containers in relatively small quantities.
Unfortunately, many vessel systems are complicated systems which require precision construction techniques and permanent, stable foundations. This necessarily drives the cost of reactor vessels systems to levels even higher than required for building-type enclosures. In exemplary prior art systems, organic waste is fed into an opening at one end of the reactor and compost is removed from the other end. The material is moved through the reactor by, for example, a complex moving floor apparatus or hydraulic ram. A cration is sometimes provided by pressurized air forced through the organic waste from air vents located throughout the moving apparatus.
Some in-vessel systems also include mixing systems, typically rotating paddles or prongs, within the compost mass. Other in-vessel systems are static. The agitation systems used with in-vessel systems are expensive, prone to wear and failure, and provide agitation at intervals that are not readily controlled with respect to the progress of the composting process.
At the present time, bioconversion processes are only marginally cost-effective. For essentially all bioconversion processes, there is at least one mechanical or chemical counterpart, and these mechanical or chemical counterparts often times require less capital or less operating expense. However, many of these mechanical or chemical counterparts are parts of much larger, higher volume systems or operations. As but one example, in the waste disposal industry there are literally millions of roll-offs and Intermodal containers which are produced in factories which have been designed to keep the cost of fabrication at a minimum level. While the bioconversion processes themselves have been optimized to both lower costs and produce valuable products for sale, it has heretofore been very difficult to provide containers which would keep costs competitive with basic roll-offs, Intermodal containers, and landfill garbage handling.
A few artisans have heretofore incorporated garbage roll-off containers and Intermodal shipping containers into the design of bioconversion systems. Exemplary of this are U.S. Pat. Nos. 6,281,001; 6,524,848; and 6,627,434; each by the present inventor and the teachings of each which are incorporated by reference. While the basic containers are then obtained at much more competitive prices, and the handling equipment is in many cases already available, there has still remained a substantial expense in retrofitting these containers.
In the prior art, one typical retrofit sequence has been the application of a solid subfloor such as a steel or other plate or layer as a replacement for or on top of the commercial wooden floor, or the application of a sealing coating onto the wooden floor. Next, a set of spacers would be provided along the length of the container, but not extending quite to an inlet end. Onto these spacers would be provided a floor which would typically be a relatively open grating of perforated metal or the like, through which ventilation air would pass up into the container interior, and also through which leachate liquid would pass down from the container interior. At the inlet end of the container, and in the gap between subfloor and floor provided by the spacers, would then be an inlet through which ventilation air would pass. Since the spacers did not extend fully, the inlet air could pass at this end between any of the spacers freely. From the inlet end, the air would then pass along the length of the container, often times forty feet in distance, and at any point along the length would pass through the openings in the floor and into the container interior. To collect the leachate, a drain would be provided at one end of the container, typically adjacent the inlet, and for exemplary purposes formed by enclosing the last two beams to form a reservoir or sump into which the leachate could pool, such as illustrated in FIGS. 4 and 5. Most typically, within the container interior would be organic matter, and the air would be slightly pressurized above ambient to pass interstitially through the organic matter. Undesirably, this retrofit requires substantial on-site labor and additional materials, the combination which substantially increases the cost of a container. In addition, the retrofit container would no longer be compatible for shipping purposes, since the new floor would necessarily be elevated several inches higher than the original floor. In addition, the elevated perforated floor would not support shipping loads.
Furthermore, as the prior art container is elongated even to forty-five and fifty-three foot lengths or more, which helps economically in processing costs, and also even at typical twenty to forty foot lengths, the air distribution through the organic matter becomes undesirably inconsistent. The present inventor has determined that, as distances from the inlet port increase, there is a measured and detrimental decrease in air flow through the mass. The twenty and forty foot lengths are undesirably long.
One area of concern with this prior art approach is the floor of the vessel. In the prior art Intermodal containers, these floors are typically special plywood which is attached onto a channel or beam floor using screws or bolts. The beam supports are commonly open on the bottom side, and a bituminous coating is typically applied to render the flooring relatively water-tight, and thereby compliant with ISO standards.
To render such container useful for bioconversion, the flooring is perforated. This may be done by adding a second “false” floor raised above the wooden flooring as described above, or by directly perforating the wooden floor. The container may then be tilled with biomass, and air introduced into the container through the floor. Leachate will simply drain out through the perforations, and may then be collected for removal. Unfortunately, the wooden floor is not resistant to bioconversion products. Perforations, nail holes and any other surface damage will lead to accelerated decomposition or failure of the floor. This surface damage may simply be a result of the insertion of the biomass, though many other processes are also known to cause surface damage, including the common practice of anchoring cargo within an Intermodal container by nailing the cargo to the container floor.
Once the container floor has been perforated, whether for ventilation or by decay, the floor is not water-tight or air tight. When a false floor is incorporated, there is substantial risk of damage to the original floor, such as accidental ignition during welding. Additionally, the container corrosion resistant coatings are necessarily damaged during installation of the false floor. Finally, the false floor requires internal space, and the container will no longer meet ISO size standards. Whether caused by perforation porosity, decreased dimension, or container damage, the end result is that containers once converted no longer meet the ISO requirements, may only be useful for bioconversion, and may have undesirably short life expectancy.
Not only has prior art conversion permanently altered the use of a container and jeopardized the container integrity, such conversion has also involved many hours of high-cost labor often provided directly at a job site. Consequently, it has heretofore been impossible to achieve the cost benefits that are associated with factory production. This has, in turn, driven the capital costs of installing a bioconversion system higher than desired.
Another cost associated with the prior art has been the biological processing time desired for the bioconversion process. Composting processes such as those described by the present inventor in the patents incorporated herein above by reference, which are among the most rapid in the industry, still require two to three weeks for an initial high temperature phase of composting to occur. There may be an additional curing period that may last two to three months. During this period, the container is being used and has heretofore been unavailable for other benefit or value. As a result, there remains a need for an improved and economical bioconversion container which is convenient, low-cost, efficient, and scalable.